Heavy ANFO is comprised of an ammonium nitrate—fuel oil (ANFO) and a water-in-oil emulsion explosive. In many cases, a density reducing material is added to the heavy ANFO such that the combination of heavy ANFO and the density reducing material has a density that is lower than the heavy ANFO. The density reducing agent is needed because the density of the heavy ANFO is too high to reliably detonate. Among the materials that have been added to the heavy ANFO to adjust the density are wood meal, saw dust , bagasse, Styrofoam etc. In many cases, the combination of heavy ANFO and a density reducing agent still does not reliably detonate.